Criminal and civil harassment are different, and charges for these actions range from misdemeanors to felonies. Usually, criminal harassment simply refers to a person who targets someone else and then behaves in a way that terrorizes, annoys or otherwise alarms the person. The behavior must be a credible threat for it to be considered harassment.
Civil harassment is not criminal in nature, but a civil harassment lawsuit can mean that you have to go to court to defend yourself. The alleged victim in a civil trial is claiming that harassment of some form has resulted in discrimination against him or her. For instance, civil lawsuits might be used in workplace discrimination cases. There are no criminal charges that go along with a civil lawsuit, since it's just the other person suing you, but you could face both a civil and criminal trial at the same time depending on your situation.
There is a large range in how a harassment claim can affect you legally speaking. Some charges are only misdemeanors, while others are high-level felonies. If you've been convicted of harassing someone in the past, then you may be more likely to face heavier penalties since it's your second or third time in court. If it's claimed that you harassed someone despite a restraining order being in place, you could also face heavier punishments if you're convicted.
Additionally, those who discriminate and harass others face heavier penalties if the victim was targeted and in a protected group. Some people in protected groups include those of different genders, religions, ages or sexual orientations. Your attorney can help you create a strong defense if you're accused of these actions.
Source: FindLaw, "Harassment," accessed March 03, 2017